In the rich text editor:
@Twooxel
In a comment:
[Twooxel](https://chowlings.com/user/Twooxel)
For Names and Avatars:
In the rich text editor:
%Twooxel
In a comment:
[![Twooxel's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/Twooxel) [Twooxel](https://chowlings.com/user/Twooxel)